Concentration Effects on Separation Selectivity in Foam Fractionation

Abstract

Removal of cadmium, copper, and nickel ions from aqueous solution by foam fractionation has been studied using a chelating surfactant, 4-dodecyl-diethylenetriamine. The rate of removal is a function of concentration of both metallic ions and surfactant. In the low concentration range for the metallic ions compared to that of the surfactant, the order of removal was found to be Cd²⁺ > Ni²⁺ > Cu²⁺. However, at higher concentrations of ions, the order becomes inverse, Cu²⁺ > Ni²⁺ > Cd²⁺. A selectivity coefficient for the separation of a specified ion from one or more ions using a chelating surfactant is shown to be dependent on the surface tension of the complex and the chelation constants. The relationship between separation selectivity of the removal of the metallic ions and concentration of both surfactant and metallic ions is discussed